Such air bag assembly units are currently used in various designs in nearly all passenger cars manufactured by the automobile industry. The costs to be incurred by motor vehicle manufacturers for the use of such units are determined, usually rather essentially, by the mounting steps to be taken for the assembly of the air bag assembly units and the time and cost factors arising herefrom. Moreover, the problem arises that based on the intensive use of the motor vehicles, the expectations on the reliability and service life are subject to increasing requirements. These requirements lead, on the one hand, to increased efforts to guarantee, for example, the reliable sealing of the gas generator placed inside the air bag assembly unit in the diffusor housing to the outside over the service life of the vehicle. The effectiveness of sealing also depends decisively on the tolerances present due to the manufacture and the construction-related means necessary as a result for compensating tolerances between the assembly units to be assembled together.
Various proposed solutions are known from the state of the art to facilitate the assembly of air bag assembly units of this class and at the same time to ensure the reliability of operation in respect to the gas tightness of the mounted air bag assembly unit.
For example, an air bag assembly unit of an occupant restraint system for motor vehicles, in which the gas generator is screwed to the diffusor housing by means of a central screw connection after the gas generator has been introduced into the diffusor housing via an installation opening, is known from EP 1 207 086 A1. The installation opening is sealed such that a flange, which is brought into contact with a stop face on the diffusor housing during mounting, is provided at the gas generator, and an elastic sealing and uncoupling ring is introduced between the flange and the diffusor housing. The tasks of fastening the gas generator, on the one hand, and of sealing it within the diffusor housing against the outer environment, on the other hand, are thus accomplished by different components, whose joining increases the effort needed for mounting and hence the manufacturing effort.
In addition, a housing for an inflatable air bag, in which the diffusor housing is embodied as a component designed integrally with the air bag housing, wherein the gas generator is directly inserted into the diffusor housing and a connection to the diffusor housing inner wall is provided for fixing same in the diffusor housing, is known, for example, from the Offenlegungsschrift DE 10 150 275 A1. Even though a reduction of the components to be mounted is brought about here compared to the state of the art mentioned at first, the positive-locking connection between the gas generator and the diffusor housing inner wall permits, however, only the use of a certain gas generator assembly unit, so that changes in the component inevitably leads to a substantially increased effort needed for making changes on the air bag housing, which has a complex design due to its function. Moreover, tolerance compensation and sealing of the diffusor housing interior space towards the outside are subject to manufacturing measurements that are to be observed accurately and thus they are again cost-intensive in respect to the manufacture of the components to be connected to one another due to the integrated design of the air bag housing.